#include <cstdio>

int number_reverse(int origin_num);

int main(int argc, char const* argv[])
{
    int a, b;
    while (scanf("%d %d", &a, &b) != EOF) {
        int reverse_a = number_reverse(a);
        int reverse_b = number_reverse(b);
        if (reverse_a + reverse_b == number_reverse(a + b))
            printf("%d\n", a + b);
        else
            printf("NO\n");
    }
    return 0;
}

int number_reverse(int origin_num)
{
    int temp_num = origin_num;
    int reverse_number = 0;
    while (temp_num != 0) {
        reverse_number = reverse_number * 10 + (temp_num % 10);
        temp_num /= 10;
    }
    return reverse_number;
}